1. Field of the Invention
The present invention relates to an optical disk reproducing device and an optical disk recording and reproducing device, and particularly to a method of making adjustment of one of an optical system and a detection system, especially focus bias adjustment, with the amplitude of a reproduced signal (hereinafter referred to as an RF signal) as an index while reproducing operation is continued without being interrupted. The optical disk reproducing device and the optical disk recording and reproducing device will hereinafter be referred to collectively as an optical disk drive, and performing reproducing operation without interrupting the reproducing operation will hereinafter be referred to as running.
2. Description of the Related Art
The optical disk drive generally causes a shift in operation center such as a focus bias or the like due to an environmental change such as a temperature rise or the like at the time of continuous operation. As a result, a reproduction margin is narrowed. It is thus desirable to perform the adjustment during the running.
However, in the current optical disk drive, the adjustment always involves an interruption of reproducing operation. As a result, the average transfer rate of the optical disk drive is decreased.
The optical disk drive has at least a reproduced signal processing device. The reproduced signal processing device has an AGC (automatic gain control) circuit for holding an RF (radio frequency) amplitude constant.
The current optical disk drive has an RF amplitude detecting circuit for making focus bias adjustment with maximization of the RF amplitude as an index, and is configured such that a controlling MCU (microprocessor control unit) can obtain the output of the RF amplitude detecting circuit. Incidentally, the RF amplitude in this case refers to the amplitude of the above-described RF signal.
It is generally known that a method of measuring the RF amplitude is performed as a method of focus bias adjustment (focus fine adjustment) of the optical disk drive, and that the focus bias adjustment is made on the basis of the RF amplitude.
In related art, the absolute value of the RF amplitude is measured to measure the RF amplitude. It is therefore necessary to turn off an automatic amplitude adjusting function (AGC). Thus, in related art, in order to make focus bias adjustment, it is necessary to turn off the AGC and interrupt reproducing operation.
An optimum focus bias value changes according to a temperature rise within the drive and other environmental variations. In the existing techniques, when focus bias adjustment is made, reproducing operation needs to be interrupted. The interruption of the reproduction may lead to degradation in drive readout performance (readout speed or the like).
Japanese Patent Laid-Open No. 2001-84608 (hereinafter referred to as Patent Document 1) describes an offline adjusting method. The present embodiment discloses a configuration enabling similar adjustment without interrupting reproducing operation.
Japanese Patent Laid-Open No. Hei 5-151589 discloses a configuration that makes focus adjustment on the basis of an RF amplitude.